1. Field of the Invention
The present invention relates to a fluid measurement device which measures the characteristics of a fluid, a method of measuring a fluid, and a fluid spacial distribution visualization device using the fluid measurement device.
2. Description of the Related Art
Recently, a fuel cell which directly extracts electricity from a hydrogen gas has been under development. As hydrogen is a gas that easily leaks, plumbing equipment which carries hydrogen is required to be highly secure. There is also a need for techniques which detect the leakage of hydrogen and identify the place of the leakage.
A fluid spacial distribution visualization device is disclosed in Nonpatent document 1 (“Improvement of olfactory video camera: gas/odor flow visualization system” by Hiroshi Ishida, Takafumi Tokuhiro, Takamichi Nakamoto and Toyosaka Morizumi, Sensors and Actuators B 83, 2002, p. 256-p. 261). This fluid spacial distribution visualization device visualizes the odor of a gas to identify the source of the gas. In this fluid spacial distribution visualization device, a sensitive film is formed on the surface of an AT-cut quartz oscillator. Thus, a resonance frequency that changes in response to the gas acting on the sensitive film is measured by using QCM gas sensors. The QCM gas sensors are one-dimensionally or two-dimensionally arranged at intervals of several cm. Measurement results of the concentrations of the gas obtained by the respective QCM gas sensors are displayed on a display screen in the form of moving images. Spacial movements of the unevenness of the gas concentrations are observed so that the movement of the gas is visualized.
A method is disclosed in Patent document 2 (“Odor sensing system” published in the journal of the Institute of Electronics, Information and Communication Engineers C-1 by Takamichi Nakamoto and Toyosaka Morizumi, April, 1994, Vol. J82-C-I, No. 4, pp. 156-pp. 164). According to this method, an odor is identified or a gas concentration is calculated from the responses of a plurality of sensor elements by, for example, a neural net computing circuit or principal component analysis. The respective sensor elements include sensitive films having gas response characteristics different from one another. Here, the odor is not exclusively the odor perceived by a human being, but the odor means a characteristic numerical value determined by the kind and amount of a gas independent from the chemical identification of the components and concentration of the gas. Outputs from the respective sensor elements including the sensitive films different in gas response characteristics from one another are measured, such that the concentration and kind of the gas are measured in a comprehensive manner. In some cases, a particular gas alone may be measured (highly selective measurement) by gas sensors including sensitive films which have the same gas response characteristics. However, it is rare that the particular gas alone is measured.